DEVELOPMENT OF A MECHANISTIC MODEL OF LIVER-METABOLISM IN THE LACTATING COW

In order to accurately predict nutrient requirements and utilization in ruminants, an assessment of hepatic nutrient utilization must be made. A mechanistic, dynamic, deterministic model of liver metabolism was constructed to integrate available data toward this end The objective of the modeling exercise was to develop a mechanistic model of ruminant liver metabolism, based on known metabolic pathways, which was capable of predicting whole-organ metabolism and simulating C-14-radiotracer kinetics. The program was written in the Advanced Continuous Simulation Language and run on a VAX computer. A fourth-order Runge-Kutta procedure was used for numerical integration. Development of kinetic arguments and subsequent parameterization relied heavily on in-vivo input:output data and underlying biochemistry. The model was evaluated using a combination of behavioral analyses, sensitivity analyses, and challenges from independent data sets.